Mantle metasomatism by melts of HIMU piclogite components: new insights from Fe-lherzolite xenoliths (Calatrava Volcanic District, central Spain)

• DOI: 10.1144/sp337.6
• Publication Date: 2010-07-14T18:12:56Z
• Authors: Gianluca Bianchini; Luigi Beccaluva; Costanza Bonadiman; Geoff M. Nowell; D. Graham Pearson; Franca Siena; Marjorie Wilson
• Keywords: Metasomatism; Xenolith

Abstract Mantle xenoliths from the Calatrava Volcanic District (CLV), central Spain, are characterized by a wide compositional range that includes lherzolites (prevalent), as well minor amounts of wehrlite, olivine (ol)-websterite and rare dunites. They generally have bulk-rock Mg# less than 89, lower any primordial mantle estimates. Intra-suite variations in modal proportions inconsistent with those predicted melting models irrespective starting composition; mineral variation diagrams show inconsistencies between CLV compositions (anomalously enriched Fe–Ti) partial material. Processes other pure melt extraction confirmed whole-rock REE (rare earth element) budget, typically LREE enrichments, La N /Yb (up to 6.7), probably related pervasive metasomatism. clinopyroxenes (cpx) display fractionated patterns upwards-convex shapes, low HREE (Tm–Lu) concentrations (typically <6× chondrite) enrichments middle–light (MREE–LREE) (Nd up 7, 5). These ‘enriched’ cpx either result re-equilibration primary an incoming melt, or represent crystallization directly metasomatic agent. The latter was plausibly generated at greater depths presence residual garnet (from peridotite eclogite materials). Separated homogeneous 87 Sr/ 86 Sr 0.7031 0.7032; 143 Nd/ 144 Nd ranges 0.51288 0.51295 (εNd 4.74–6.07) 176 Hf/ 177 Hf is 0.28302–0.28265 (εHf −3.6 9.0). Unlike alpine-type peridotites Iberian occurrences, which composition depleted (DM) (EM), approach HIMU end member, genesis interpreted long-term recycling oceanic basalts/gabbros (or their eclogitic equivalent) via ancient subduction. A model proposed for evolution under Iberia, where sublithospheric convective instabilities – possibly triggered neighbouring subduction along Betic collisional belt could remobilized deep domains ‘transition zone’ (410–660 km), may include relicts older subducted slabs. Within these domains, coexistence referred ‘piclogite’ association, eclogites preferentially generating Fe–Ti rich melts isotopic signature infiltrates metasomatizes shallower lithospheric mantle.